A-21978C10, known as Daptomycin, is a 13-amino acids cyclic peptide antibiotic of formula (I)

containing a n-decanoyl side chain linked to the N-terminal tryptophan.
Daptomycin is produced by submerged fermentation of Streptomyces roseosporus, in particular strains NRRL 11379 (ATCC 31568) and NRRL 15998, as well as any mutants, variants and recombinants thereof.
The production of Daptomycin in submerged culture was first disclosed in U.S. Pat. No. 4,331,594 and U.S. Pat. No. 4,800,157.
U.S. Pat. No. 4,885,243 discloses the preparation of Daptomycin by fed-batch fermentation, in which decanoic acid, used as source of the n-decanoyl side chain, is fed as a solution in an organic solvent, namely methyl oleate. The presence of the solvent in the feeding solution is necessary, because decanoic acid is a waxy solid at the fermentation temperature and only solutions containing at least 50% solvent are sufficiently fluid to be fed. Nevertheless, even in the presence of a solvent, at temperatures lower that 25° C. it is difficult to maintain a constant and homogeneous feeding, because decanoic acid may separate from the solution or form flakes and clumps. Decanoic acid exerts a toxic effect on the bacteria and for this reason the feeding rate must be kept under strict control.